This research project deals with immunochemical studies on human placental alkaline phosphatase variants obtained from placentae and cancer patients. Progress during the past year has included definition of antigenic sites specific for the cancer variant enzyme by using absorbed rabbit antisera and monoclonal antibodies. Objectives for the current year include continuing to analyze these variant enzymes by generating other monoclonal antibodies and initiating studies on the chemical structures of these enzymes. The occurrence of this enzyme on membrane fragments in cancer patient ascites fluids has been of some interest to us, and studies on this enzyme form are being continued. Nude mice carrying a variety of gynecological tumors which have placental-type phosphatase are also being studied.